unbeknown vs unknown

unbeknown is not a noun while unknown is a noun.

Word	Noun	Adjective	Verb	Adverb
unbeknown	No	Yes	No	Yes
unknown	Yes	Yes	No	No

unbeknown (noun)	unknown (noun)
	a variable whose values are solutions of an equation
	an unknown and unexplored region
	anyone who does not belong in the environment in which they are found

unbeknown (adjective)	unknown (adjective)
(usually used with `to') occurring or existing without the knowledge of	not known
	being or having an unknown or unnamed source
	not famous or acclaimed
	not known before
	not known to exist

unbeknown (adverb)	unknown (adverb)
without someone's knowledge